"""
TencentBlueKing is pleased to support the open source community by making
蓝鲸智云PaaS平台社区版 (BlueKing PaaSCommunity Edition) available.
Copyright (C) 2017-2018 THL A29 Limited,
a Tencent company. All rights reserved.
Licensed under the MIT License (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at http://opensource.org/licenses/MIT
Unless required by applicable law or agreed to in writing,
software distributed under the License is distributed on
an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
either express or implied. See the License for the
specific language governing permissions and limitations under the License.
"""

import base64
import string
import random
import hashlib
import time
import struct
import socket
import xml.etree.cElementTree as ET

from Crypto.Cipher import AES

from . import ierror

"""
关于Crypto.Cipher模块，ImportError: No module named 'Crypto'解决方案
请到官方网站 https://www.dlitz.net/software/pycrypto/ 下载pycrypto。
下载后，按照README中的“Installation”小节的提示进行pycrypto安装。
"""


class FormatException(Exception):
    pass


def throw_exception(message, exception_class=FormatException):
    """my define raise exception function"""
    raise exception_class(message)


class SHA1:
    """计算企业微信的消息签名接口"""

    def get_sha1(self, token, timestamp, nonce, encrypt):
        """用SHA1算法生成安全签名
        @param token:  票据
        @param timestamp: 时间戳
        @param encrypt: 密文
        @param nonce: 随机字符串
        @return: 安全签名
        """
        try:
            sortlist = [token, timestamp, nonce, encrypt]
            sortlist.sort()
            sha = hashlib.sha1()
            sha.update("".join(sortlist).encode("utf-8"))
            return ierror.WXBizMsgCrypt_OK, sha.hexdigest()
        except Exception as e:
            print(e)
            return ierror.WXBizMsgCrypt_ComputeSignature_Error, None


class XMLParse:
    """提供提取消息格式中的密文及生成回复消息格式的接口"""

    # xml消息模板
    AES_TEXT_RESPONSE_TEMPLATE = """<xml>
<Encrypt><![CDATA[%(msg_encrypt)s]]></Encrypt>
<MsgSignature><![CDATA[%(msg_signaturet)s]]></MsgSignature>
<TimeStamp>%(timestamp)s</TimeStamp>
<Nonce><![CDATA[%(nonce)s]]></Nonce>
</xml>"""

    def extract(self, xmltext):
        """
        提取出xml数据包中的加密消息
        @param xmltext: 待提取的xml字符串
        @return: 提取出的加密消息字符串
        """
        try:
            xml_tree = ET.fromstring(xmltext)
            encrypt = xml_tree.find("Encrypt")
            touser_name = xml_tree.find("ToUserName")
            return ierror.WXBizMsgCrypt_OK, encrypt.text, touser_name.text
        except Exception as e:
            print(e)
            return ierror.WXBizMsgCrypt_ParseXml_Error, None, None

    def generate(self, encrypt, signature, timestamp, nonce):
        """生成xml消息
        @param encrypt: 加密后的消息密文
        @param signature: 安全签名
        @param timestamp: 时间戳
        @param nonce: 随机字符串
        @return: 生成的xml字符串
        """
        resp_dict = {
            'msg_encrypt': encrypt,
            'msg_signature': signature,
            'timestamp': timestamp,
            'nonce': nonce,
        }
        resp_xml = self.AES_TEXT_RESPONSE_TEMPLATE % resp_dict
        return resp_xml


class PKCS7Encoder():
    """提供基于PKCS7算法的加解密接口"""

    block_size = 32

    def encode(self, text):
        """ 对需要加密的明文进行填充补位
        @param text: 需要进行填充补位操作的明文
        @return: 补齐明文字符串
        """
        text_length = len(text)
        # 计算需要填充的位数
        amount_to_pad = self.block_size - (text_length % self.block_size)
        if amount_to_pad == 0:
            amount_to_pad = self.block_size
        # 获得补位所用的字符
        pad = chr(amount_to_pad)
        return text + pad * amount_to_pad

    def decode(self, decrypted):
        """删除解密后明文的补位字符
        @param decrypted: 解密后的明文
        @return: 删除补位字符后的明文
        """
        pad = ord(decrypted[-1])
        if pad < 1 or pad > 32:
            pad = 0
        return decrypted[:-pad]


class Prpcrypt(object):
    """提供接收和推送给企业微信消息的加解密接口"""

    def __init__(self, key):

        # self.key = base64.b64decode(key+"=")
        self.key = key
        # 设置加解密模式为AES的CBC模式
        self.mode = AES.MODE_CBC

    def encrypt(self, text, corpid):
        """对明文进行加密
        @param text: 需要加密的明文
        @return: 加密得到的字符串
        """
        # 16位随机字符串添加到明文开头
        text = self.get_random_str() + struct.pack("I", socket.htonl(len(text))) + text + corpid
        # 使用自定义的填充方式对明文进行补位填充
        pkcs7 = PKCS7Encoder()
        text = pkcs7.encode(text)
        # 加密
        cryptor = AES.new(self.key, self.mode, self.key[:16])
        try:
            ciphertext = cryptor.encrypt(text)
            # 使用BASE64对加密后的字符串进行编码
            return ierror.WXBizMsgCrypt_OK, base64.b64encode(ciphertext)
        except Exception as e:
            print(e)
            return ierror.WXBizMsgCrypt_EncryptAES_Error, None

    def decrypt(self, text, corpid):
        """
        对解密后的明文进行补位删除
        @param text: 密文
        @return: 删除填充补位后的明文
        """
        try:
            cryptor = AES.new(self.key, self.mode, self.key[:16])
            # 使用BASE64对密文进行解码，然后AES-CBC解密
            plain_text = cryptor.decrypt(base64.b64decode(text))
        except Exception as e:
            print(e)
            return ierror.WXBizMsgCrypt_DecryptAES_Error, None
        try:
            pad = plain_text[-1]
            content = plain_text[16:-pad]
            xml_len = socket.ntohl(struct.unpack("I", content[: 4])[0])
            xml_content = content[4: xml_len + 4]
        except Exception as e:
            print(e)
            return ierror.WXBizMsgCrypt_IllegalBuffer, None

        return 0, xml_content

    def get_random_str(self):
        """
        随机生成16位字符串
        @return: 16位字符串
        """
        rule = string.ascii_letters + string.digits
        str = random.sample(rule, 16)
        return "".join(str)


class WXBizMsgCrypt(object):
    # 构造函数
    # @param s_token: 企业微信后台，开发者设置的Token
    # @param sEncodingAESKey: 企业微信后台，开发者设置的EncodingAESKey
    # @param s_corp_id: 企业号的CorpId
    def __init__(self, s_token, sEncodingAESKey, s_corp_id):
        try:
            self.key = base64.b64decode(sEncodingAESKey + "=")
            assert len(self.key) == 32
        except Exception:
            throw_exception("[error]: EncodingAESKey unvalid !", FormatException)

        self.m_s_token = s_token
        self.m_s_corp_id = s_corp_id

        # 验证URL
        # @param s_msg_signature: 签名串，对应URL参数的msg_signature
        # @param s_timestamp: 时间戳，对应URL参数的timestamp
        # @param s_nonce: 随机串，对应URL参数的nonce
        # @param sEchoStr: 随机串，对应URL参数的echostr
        # @param s_reply_echo_str: 解密之后的echostr，当return返回0时有效
        # @return：成功0，失败返回对应的错误码

    def verify_url(self, s_msg_signature, s_timestamp, s_nonce, sEchoStr):
        sha1 = SHA1()
        ret, signature = sha1.get_sha1(self.m_s_token, s_timestamp, s_nonce, sEchoStr)
        if ret != 0:
            return ret, None
        if not signature == s_msg_signature:
            return ierror.WXBizMsgCrypt_ValidateSignature_Error, None
        pc = Prpcrypt(self.key)
        ret, s_reply_echo_str = pc.decrypt(sEchoStr, self.m_s_corp_id)
        return ret, s_reply_echo_str

    def encrypt_msg(self, s_reply_msg, s_nonce, timestamp=None):
        # 将企业回复用户的消息加密打包
        # @param s_reply_msg: 企业号待回复用户的消息，xml格式的字符串
        # @param s_timestamp: 时间戳，可以自己生成，也可以用URL参数的timestamp,如为None则自动用当前时间
        # @param s_nonce: 随机串，可以自己生成，也可以用URL参数的nonce
        # sEncryptMsg: 加密后的可以直接回复用户的密文，包括msg_signature, timestamp, nonce, encrypt的xml格式的字符串,
        # return：成功0，sEncryptMsg,失败返回对应的错误码None
        pc = Prpcrypt(self.key)
        ret, encrypt = pc.encrypt(s_reply_msg, self.m_s_corp_id)
        if ret != 0:
            return ret, None
        if timestamp is None:
            timestamp = str(int(time.time()))
        # 生成安全签名
        sha1 = SHA1()
        ret, signature = sha1.get_sha1(self.m_s_token, timestamp, s_nonce, encrypt)
        if ret != 0:
            return ret, None
        xml_parse = XMLParse()
        return ret, xml_parse.generate(encrypt, signature, timestamp, s_nonce)

    def decrypt_msg(self, s_post_data, s_msg_signature, s_timestamp, s_nonce):
        # 检验消息的真实性，并且获取解密后的明文
        # @param s_msg_signature: 签名串，对应URL参数的msg_signature
        # @param s_timestamp: 时间戳，对应URL参数的timestamp
        # @param s_nonce: 随机串，对应URL参数的nonce
        # @param s_post_data: 密文，对应POST请求的数据
        #  xml_content: 解密后的原文，当return返回0时有效
        # @return: 成功0，失败返回对应的错误码
        # 验证安全签名
        xml_parse = XMLParse()
        ret, encrypt, _ = xml_parse.extract(s_post_data)
        if ret != 0:
            return ret, None
        sha1 = SHA1()
        ret, signature = sha1.get_sha1(self.m_s_token, s_timestamp, s_nonce, encrypt)
        if ret != 0:
            return ret, None
        if not signature == s_msg_signature:
            return ierror.WXBizMsgCrypt_ValidateSignature_Error, None
        pc = Prpcrypt(self.key)
        ret, xml_content = pc.decrypt(encrypt, self.m_s_corp_id)
        return ret, xml_content
